Assuming the down velocity of the stationary phase is (QL), and that the retention volume (V'r) is given by V'r = KVL (see Plate Theory and Extensions ) then if
then solute (A) will pass up the column.
Conversely, if 
then solute (A) will pass down the column.
The conditions for the continuous separation of substances (A), (B) and (C) are now clear.
Courtesy of Butterworths Scientific Publications Ltd. [Ref. 10]
Figure 26TheMovingBedContinuous Gas-Liquid Chromatography System for Separating Pure Benzene from Coal Gas
